negroni

一.简介

negroni是一个web中间件,方便使用net/http的库;它实现了http.Handle接口,兼容http.Handle.

获取方式:go get github.com/urfave/negroni

negroni的主要的结构:

type Negroni struct {
	middleware middleware //节点结构
	handlers   []Handler    //对应的中间件的执行链
}

type middleware struct {
	handler Handler
	next    *middleware
}

type Handler interface {
	ServeHTTP(rw http.ResponseWriter, r *http.Request, next http.HandlerFunc)
}

type HandlerFunc func(ResponseWriter, *Request)

二.使用

1)简单的demo(向浏览器输出):

func main() {
	n := negroni.Classic()
	n.UseHandler(http.HandlerFunc(myHandler))
	n.Run()
}

func myHandler(rw http.ResponseWriter, r *http.Request) {
	io.WriteString(rw, "Hello World")
}

Classic()返回一个Negroni实例(会添加异常恢复,日志和静态文件服务器三个中间件)

UseHandler()将Handle添加到Negroni的实例中的执行链的最后面(可以参考UseHandler()里面调用的build())

func build(handlers []Handler) middleware {
	var next middleware

	if len(handlers) == 0 {
		return voidMiddleware()
	} else if len(handlers) > 1 {
		next = build(handlers[1:])
	} else {
		next = voidMiddleware()
	}

	return middleware{handlers[0], &next}
}

Run()和ListenAndServe()一样.当然也可以自己使用Negroni的New()定义自己的Negroni实例

2)中间件的添加:

func (n *Negroni) Use(handler Handler)
func (n *Negroni) UseFunc(handlerFunc func(rw http.ResponseWriter, r *http.Request, next http.HandlerFunc))
func (n *Negroni) UseHandler(handler http.Handler)
func (n *Negroni) UseHandlerFunc(handlerFunc func(rw http.ResponseWriter, r *http.Request))

这四个函数可以将中间件动态添加到执行链中,后三个函数最终都会调用Use:

func (n *Negroni) Use(handler Handler) {
	if handler == nil {
		panic("handler cannot be nil")
	}

	n.handlers = append(n.handlers, handler)
	n.middleware = build(n.handlers)
}

 

3)执行链的使用:

Negroni自定义了Handler,与http.Handler唯一不同是多了next参数,各个中间件自己判断是否使用next()执行下一个中间件

测试demo(模拟登陆鉴权):

func main() {
 //流程:注册myHandlerOne模拟鉴权,根据path判断是否执行myHandleTwo

	n := negroni.Classic()
	n.UseFunc(myHandlerOne)
	mux := http.NewServeMux()
	mux.Handle("/index", http.HandlerFunc(myHandlerTwo))
	n.UseHandler(mux)
	n.Run()
}

func myHandlerOne(rw http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
	io.WriteString(rw, "login in\n")
	fmt.Println(r.URL.Path)
	if r.URL.Path == `/index` {
		next(rw, r)
	}

}

func myHandlerTwo(rw http.ResponseWriter, r *http.Request) {
	io.WriteString(rw, "Hello World")
}

使用Negroni这种方式可以控制中间件的执行,可以中断